Process of refining hydrocarbon oils



ill

Patented Jan. 2, 1940 UNITED STATES PROCESS OF REFENING HYDROCARBON OILSDavid F. Gould, Riverton, N. 3., assignor to The Barrett Company, NewYork, N. Y, a corporation of New Jersey No Drawing. Application August2, 1937, Serial No. 156,647

3 Claims.

This invention relates to the refining of crude hydrocarbon oils andparticularly to the refining of oils obtained in the gasification orcarb-onization of coal or production of carburetted water gas, such as,for example, coke oven light oils, drip oils, coal tar and water gas tardistillates, etc, which are hereinafter referred to as aromatichydrocarbon oils.

It is well known to refine hydrocarbon oils by treating them withconcentrated sulfuric acid (66 Be.) to remove tarry and gum-formingconstituents. This method is not only wasteful, due to a substantialloss of oil which is sulfonated by the acid, but the concentratedacid'causes by-products to be formed, which remain in the oil and, onstorage, produce color changes in the oil. It has been proposed to treathydrocarbon oils with sulfuric acid of a strength below 66 Be. Accordingto this proposal, the oil is treated with sulfuric acid which may be ofa strength below 60 B., after which the acid is drawn off, the oilneutralized with caustic soda, and the purified oil removed by, steamdistillation.

I have made the surprising discovery that by treating the crudehydrocarbon oil with sulfuric acid of a strength below that at whichsulfonation of the oil readily takes place and then distilling the oilfrom the mixture without first removing the acid, refined oil isobtained which is superior with respect to its color stability onstorage to oils heretofore produced by the acid refining of crudehydrocarbon oils.

According to my invention, hydrocarbon oils, such as benzol, toluol,xylol, or mixtures of such oils, solvent naphtha, drip oils, etc., aretreated with a sulfuric acid solution containing less than 70% H2804 andthereafter, without removing the sulfuric acid, the mixture is distilledto drive off the refined oil therefrom. The oil-acid mixture is heatedto facilitate the reaction of the acid upon the unsaturated compounds inthe oil. This heating may be accomplished in bringing the mixture up tothe distillation temperature; or if desired the mixture may be slowlyheated to a point below the distillation temperature and maintained atsuch temperature until the action of the acid on the unsaturatedcompounds is completed; but preferably the heating is accomplished byrefluxing the mixture until the action of the acid on the unsaturatedcompounds is completed so that substantially complete sep aration of thereaction products of such unsaturates may then be effected. After therefined oil is distilled from the mixture, it is neutralized to removethe small amount of acidic impurities which come over with the oilduring the distillation. The polymerizable constituents of the crude oilare polymerized by the sulfuric acid and the products remain in thevessel as a liquid or low melting polymer, and may be recovered in anysuitable manner.

According to the preferred embodiment of my invention, the crudehydrocarbon oil is refluxed with a sulfuric acid solution containingbetween about and about 70% H2804, preferably between about and aboutH2804. The amount of acid used and the time of refluxing are to someextent dependent on one another, for if a relatively large amount ofacid; e. g., 20% by volume of the .oil, is used, the time may berelatively short; e. g., hour, while a relatively small amount of acid;e. g., 7% by volume of oil, may require a relatively long refluxingtime; c. g., i'or more hours. The use of the larger amount of acid ispreferred and the excess is recoverable for reuse since it is not wastedin sulfonation of the oil as is the case when 66 Be. acid is used. Thetemperature at which the mixture is refluxed is regulated according tothe boiling point of the lowest boiling constituent of the mixture.Thus, for crude solvent naphtha or other relatively low boiling oils,the temperature is determined by the boiling point of the oil e. g., C.for crude drip oil solvent naphtha, while in the case of the higherboiling oils, such as hiflash naphtha, the refluxing temperature islimited by the boiling point of the acid used; c. g., 123 C. for 50%acid and 165 C. for 70% acid. After the acid treatment is finished, inthe case of higher boiling oils the mixture is held, at a temperaturejust below the boiling point of the acid used and is steam distilled atthis temperature to remove the volatile oil from the mixture withoutcarrying over substantial amounts of acid.

The following example is illustrative of this invention:

Example 1.5 parts by volume of crude hiflash naphtha obtained from dripoil (the oil condensed in mains through which coal distillation gas orcarburetted water gas is passed) having a boiling range between about150 and about 206 C. were refluxed for hour with 1 part by volume of 65%sulfuric acid. Without removing the acid, the mixture was steamdistilled at a still temperature of to C., the resultant distillate wasneutralized with caustic soda solution and then fractionated intosolventnaphtha and hiflash naphtha fractions. These fractions showedsatisfactory color stability on storage for nine months, and had acidwash tests (hereinafter described) of 10 and 6, respectively.

While the above example describes a batch operation, the invention canbe carried out continuously by treating the oil with acid in acountercurrent scrubber and continuously distilling purified oil fromthe mixture after a suitable time of contact.

The wash test hereinabove mentioned is de scribed by Weiss, Industrialand Engineering Chemistry, Vol. 10, page 1008 (1918). In this method ofgrading refined oils, the oil is washed With acid and the color of theacid layer after the washing is compared with standard colors designatedby numbers from to 14, or in a second series by numbers from 0-1 to(3-10. The color No. 14 in the former series corresponds to 0-7 in thesecond series. Thus the color of the acid used in testing the oil issaid to vary progressively from No. 0 to No. 14, 0-8, 0-9, and

0-10, in varying from water-white through yellow to brown.

The following example illustrates the superiority of the process of thisinvention over previous processes for refining crude hydrocarbon oilswith respect to removal of substances darkened by concentrated sulfuricacid:

Example 2.5 parts by volume of crude solvent naphtha having a boilingrange between about 112 and about 187 C. were refluxed for hour with 1part by volume of 65% sulfuric acid. The refined oil was then distilledfrom the mixture without removing excess acid and the distillateneutralized and. fractionated into solvent naphtha and hiflash naphthafractions. These fractions showed acid wash tests of 8+ and 7,respectively. The same crude oil was then refluxed with the sameproportion of acid as above for 2 hours, but excess acid was removed andthe oil neutralized before distillation. The solvent naphtha and hiflashnaphtha fractions obtained on fractionation of the distillate showedacid wash tests of 10 and 14+, respectively.

A further example illustrates the superiority of the process of thisinvention over previous processes for refining crude hydrocarbon oilswith respect to color stability of the refined oil on storage:

Emample 3.-The same crude solvent naphtha as used in Example 2 wasrefluxed for A9, hour with the same proportion of 65% sulfuric acid, therefined oil distilled from the mixture without removing excess acid andthe distillate neutra1- ized; on fractionation the distillate gavefractions withinthe range ofcolumn temperatures of 125 to 185 C. Thesefractions showed good color stability on storage for nine months exposedto diffused light. On the other hand, when the same crude oil wasrefined by the usual method, wherein it was treated with concentratedsulfuric acid (about 93% the acid sludge removed and the oilneutralized, washed with water and fractionally distilled, thedistillates obtained averaged 3% less in volume than those obtained bythe process of this invention, and on storage for one month, un-

der the same conditions as above, darkened in color and showed aprecipitation of material of a soft resinous character.

The above tests show the superiority of the oil refining process of thisinvention. One possible explanation for the improved results obtained isthat during the distillation of acid-treated oils resulting from theordinary method of. refining, some of the constituents of the oildecompose, producing distilla-ble unsaturates which tend to discolor theoil distillate on storage; where, however, the oil is distilled, as inaccordance with this invention, in the presence of the acid, suchunsaturates are acted on by the acid and converted to forms which do notdistill over, a distillate product of improved wash test and colorstability being thus obtained.

From the above it will be noted that by this invention refinedhydrocarbon oils may be produced which show either a lower acid washtest or improved color stability, or both, as compared with oils refinedby prior methods. Moreover, this invention results in a saving of oilbecause substantially less sulfonation occurs than is the case when acidof 66 Be. strength is used. Furthermore, this invention permits therefining of the oil with the consumption of less acid and substantiallyreduces the time necessary as compared to prior methods.

Since certain changes may be made in carrying out the above processwithout departing from the scope of the invention, it is intended thatall matter contained in the above description shall be interpreted asillustrative and not in a, limiting sense.

I claim:

' l. A process of refining a hydrocarbon oil from the group consistingof benzol, toluol, xylol, or mixtures thereof, solvent naphtha and dripoil which comprises adding sulfuric acid of a strength not exceedingabout 70% H2804 to said oil, heating the resulting mixture in the liquidphase, thereafter, without neutralizing acidic constituents in the oil,distilling off the oil, and then neutralizing acidic constituents in theresultant oil distillate.

v 2. A process of refining an aromatic hydrocarbon oil which comprisesadding sulfuric acid of a strength not exceeding about 70% H2804 to saidoil, heating the resulting mixture in the liquid phase and, withoutneutralizing acidic constituents inthe oil, distilling off the oil andthen neutralizing acidic constituents in the resultant oil distillate.

3. A process of refining a hydrocarbon oil from the group consisting ofbenzol, toluol, xylol, or mixtures thereof, solvent naphtha and drip oilwhich comprises adding sulfuric acid containing between about 50% andabout 70% H2804 to said oil, heating the resulting mixture in the liquidphase, thereafter, without neutralizing acidic constituents in the oil,distilling off the oil and then neutralizing acidic constituents in theresultant oil distillate.

DAVID F. GOULD.

